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Kazuo Awai

Publications and source records attributed to Kazuo Awai.

At least 19 recordsLinked to original sources
PubMed2007

Prediction of aortic peak enhancement in monophasic contrast injection protocols at multidetector CT: phantom and patient studies.

PURPOSE: The aim of this study was to investigate whether it is possible to predict aortic peak enhancement (APE) from the contrast dose and injection rate. MATERIALS AND METHODS: We first undertook an experimental study using a flow phantom that simulates the human circulation. We delivered 90-150 ml of iomeprol-350 at various injection rates and measured the APE values of the simulated aorta. In our clinical study we randomized 20 patients into four groups. In groups A, B, and C the iodine dose per kilogram of body weight (BW) ranged from 450 to 600 mg, and the injection duration was fixed at 30 s; group D received 450 mg/kg over 25 s. We then measured APE in all patients at the whole aorta, averaged the three highest values, and took the result as APE. RESULTS: In the phantom study, the decision coefficient for the best-fit equation obtained by multiple regression analysis of the relation between the iodine dose and injection rate and the simulated APE was high (0.93). In the patient study, the predicted APE values almost corresponded with the averaged APE values when we applied the fitness equation. CONCLUSION: Using our fitness equation, APE on contrast-enhanced computed tomography can be predicted from the iodine dose and the contrast injection rate per patient weight.

Adult↗
PubMed2006

In vitro evaluation of metallic coronary artery stents with sub-millimeter multi-slice computed tomography using an ECG-gated cardiac phantom: relationship between in-stent visualization and stent type.

The aim of this experimental study was to investigate visualization of various coronary artery stents with sub-millimeter multi-slice spiral computed tomography (MSCT) using a cardiac physical phantom. Four 3-mm stents of various designs were implanted in tubes with an inner diameter of 3 mm to simulate coronary artery. Stents were placed on a cardiac phantom and scanned at different heart rates. Retrospective ECG-gated adaptive segmental reconstruction technique was employed. Profile curves across longitudinal curved planar reconstruction images of the stents were generated. From the profile curve, the full width at half maximum was defined as the stent lumen index. The effect of heart rate and stent type on the stent lumen index was evaluated. Visual evaluation for each stent at various heart rates was also performed. The heart rate had no significant effect on in-stent visualization. However, in-stent visualization differed significantly for the various stent types for both profile curve analysis and visual evaluation (the Tukey-Kramer multiple comparisons test). Multiple regression analysis indicated that strut thickness, especially minimal strut thickness, was the significant influencing factor for the in-stent visualization. On the basis of four stent models examined it would appear that visualization of the coronary stent lumen varies depending on the stent type, but not on the heart rate. Stents with slim struts are preferable for in-stent evaluation with multi-slice spiral computed tomography.

Biocompatible Materials↗
PubMed2006

Monitoring therapeutic responses of primary bone tumors by diffusion-weighted image: Initial results.

The purpose of our study was to investigate whether quantitative diffusion-weighted images (DWI) were useful for monitoring the therapeutic response of primary bone tumors. We encountered 18 osteogenic and Ewing sarcomas. Magnetic resonance (MR) images were performed in all patients before and after therapy. We measured the apparent diffusion coefficient (ADC) values, contrast-to-noise ratio (CNR), and tumor volume of the bone tumors pre- and posttreatment. We determined change in ADC value, change in CNR on T2-weighted images (T2WI), change in CNR on gadopentetate dimeglumine (Gd)-T1-weighted images (Gd-T1WI), and change in tumor volume. The bone tumors were divided into two groups: group A was comprised of tumors with less than 90% necrosis after treatment and group B of tumors at least with 90%. Changes in ADC value, tumor volume, and CNR were compared between the groups. Change in the ADC value was statistically greater in group B than that in the group A (p = 0.003). There was no significant difference in the changes in CNR on T2WI (p = 0.683), in CNR on Gd-T1WI (p = 0.763), and tumor volume (p = 0.065). The ADC value on DWI is a promising tool for monitoring the therapeutic response of primary bone sarcomas.

Adolescent↗
PubMed2006

Automated hepatic volumetry for living related liver transplantation at multisection CT.

PURPOSE: To prospectively compare in vivo hepatic automated volumetry with manual volumetry and measured liver volume. MATERIALS AND METHODS: The study was conducted in accordance with the guidelines of the Institutional Review Board of Kumamoto University (Japan). Patient informed consent was obtained. Preoperative multisection computed tomography (CT) was performed in 35 consecutive patients (21 men, 14 women; mean age, 42.8 years; range, 28-72 years) with hepatic disease awaiting living related liver transplantation. The CT scans covered the entire liver at a section thickness of 2.5 mm. Liver volume was estimated by using both the automated and the manual methods. Actual liver weight was obtained for all patients and was converted to hepatic volume on the basis of a predetermined relationship between actual liver weight and volume. Processing time required for both methods was also recorded. Two-tailed paired t test, correlation coefficient, and Bland-Altman tests were used for statistical analyses. RESULTS: Mean liver weight was 881.7 g +/- 249.8 (standard deviation), and mean measured liver volume was 956.00 cm(3) +/- 280.10. Volumetry performed with the automated and manual methods provided liver volumes of 982.99 cm(3) +/- 301.98 and 937.10 cm(3) +/- 301.31, respectively. There was good correlation between measured and estimated volumes obtained with the automated method (r = 0.792, P < .01). The manual and automated methods required 32.8 minutes +/- 6.9 and 4.4 minutes +/- 1.9, respectively. CONCLUSION: The automated method reduced the time required for volumetry of the liver and provided acceptable measurements.

Adult↗
PubMed2006

[Comparison of LCD and CRT monitors for detection of pulmonary nodules and interstitial lung diseases on digital chest radiographs by using receiver operating characteristic analysis].

Soft copy reading of digital images has been practiced commonly in the PACS environment. In this study, we compared liquid-crystal display (LCD) and cathode-ray tube (CRT) monitors for detection of pulmonary nodules and interstitial lung diseases on digital chest radiographs by using receiver operating characteristic (ROC) analysis. Digital chest images with a 1000x1000 matrix size and a 8 bit grayscale were displayed on LCD/CRT monitor with 2M pixels in each observer test. Eight and ten radiologists participated in the observer tests for detection of nodules and interstitial diseases, respectively. In each observer test, radiologists marked their confidence levels for diagnosis of pulmonary nodules or interstitial diseases. The detection performance of radiologists was evaluated by ROC analyses. The average Az values (area under the ROC curve) in detecting pulmonary nodules with LCD and CRT monitors were 0.792 and 0.814, respectively. In addition, the average Az values in detecting interstitial diseases with LCD and CRT monitors were 0.951 and 0.953, respectively. There was no statistically significant difference between LCD and CRT for both detection of pulmonary nodules (P=0.522) and interstitial lung diseases (P=0.869). Therefore, we believe that the LCD monitor instead of the CRT monitor can be used for the diagnosis of pulmonary nodules and interstitial lung diseases in digital chest images.

Data Display↗
PubMed2006

Multi-slice CT demonstration of sinus of Valsalva rupture.

Aneurysms of the sinus of Valsalva are rare. We report here the case of a 56-year-old man with a ruptured aneurysm of sinus of Valsalva with flow into the right ventricle which was diagnosed non-invasively by 64-row multi-slice computed tomographic (CT) imaging. The right sinus of Valsalva aneurysm rupturing into the right ventricular outflow region might be silent or symptomless in many cases. The patient also had mild symptom. For anatomical demonstration, contrast-enhanced CT was performed. Although the ruptured sinus of Valsalva was initially diagnosed by echocardiography, CT images did give our surgeons a better three-dimensional appreciation when surgical repair was performed. Multi-slice CT imaging should be considered the technique of choice for both diagnosis and follow-up examination of the aneurysm of sinus of Valsalva and its rupture.

Aortic Rupture↗
PubMed2006

Coronary arterial malformation depicted at multi-slice CT angiography.

We present a case of a 57-year-old woman with an unremarkable medical history except for a continuous cardiac murmur at the left second and third interspaces. Transthoracic echocardiography revealed an unusual chamber in front of the heart. To evaluate the precise anatomy of this abnormality, multi-slice computed tomographic (MSCT) imaging was performed. MSCT angiography with retrospective ECG gating showed a coronary arterial malformation with fistulous communications to the coronary artery, pulmonary artery and the root of aorta. Images from MSCT coronary angiography can be helpful in understanding the tortuous configuration of the coronary arterial malformation.

Aorta↗
PubMed2006

Pulmonary nodules: estimation of malignancy at thin-section helical CT--effect of computer-aided diagnosis on performance of radiologists.

PURPOSE: To evaluate the effect of a computer-aided diagnosis (CAD) system on the diagnostic performance of radiologists for the estimation of the malignancy of pulmonary nodules on thin-section helical computed tomographic (CT) scans. MATERIALS AND METHODS: The institutional review board approved use of the CT database; informed specific study-related consent was waived. The institutional review board approved participation of radiologists; informed consent was obtained from all observers. Thirty-three (18 malignant, 15 benign) pulmonary nodules of less than 3.0 cm in maximal diameter were evaluated. Receiver operating characteristic (ROC) analysis with a continuous rating scale was used to compare observer performance for the estimation of the likelihood of malignancy first without and then with the CAD system. The participants were 10 board-certified radiologists and nine radiology residents. RESULTS: For all 19 participants, the mean area under the best-fit ROC curve (A(z)) values achieved without and with the CAD system were 0.843 +/- 0.097 (standard deviation) and 0.924 +/- 0.043, respectively. The difference was significant (P = .021). The mean A(z) values achieved without and with the CAD system were 0.910 +/- 0.052 and 0.944 +/- 0.040, respectively, for the 10 board-certified radiologists (P = .190) and 0.768 +/- 0.078 and 0.901 +/- 0.036, respectively, for the nine radiology residents (P = .009). CONCLUSION: Use of the CAD system significantly (P = .009) improved the diagnostic performance of radiology residents for assessment of the malignancy of pulmonary nodules; however, it did not improve that of board-certified radiologists.

Adenocarcinoma↗
PubMed2006

Mutidetector-row CT and quantitative gated SPECT for the assessment of left ventricular function in small hearts: the cardiac physical phantom study using a combined SPECT/CT system.

UNLABELLED: The aim of this study was to compare results of left ventricular (LV) function obtained by quantitative gated single-photon emission tomography (QGS) and multidetector-row spiral computed tomography (MDCT) with reference parameters using an electrocardiogram-gated cardiac physical phantom. The phantom study was performed using a combined SPECT/CT system. Flexible membranes formed the inner and outer walls of the simulated LV. The stroke volume was adjusted (45 mL or 58 mL) and the fixed 42-mL end-systolic volume (ESV) produced two different volume combinations. The LV function parameters were estimated by means of MDCT and QGS. Differences in true and measured volumes were compared among CT with a reconstructed image thickness of 2.5 mm and 5.0 mm and QGS volumetric values. Each scan was repeated three-times. The estimation of LV volumes using both QGS and MDCT analyses were reproducible very well. QGS overestimated ejection fraction (EF) by approximately 20%; MDCT volumetry overestimated EF by approximately 5% in each volume setting. The differences in true and measured values for EF and ESV obtained with QGS were significantly greater than obtained with MDCT. CONCLUSION: MDCT provides a reliable estimation of functional LV parameters, whereas QGS tends to significantly overestimate the EF in small hearts.

Analysis of Variance↗
PubMed2006

Evaluation of diffusion-weighted imaging for the differential diagnosis of poorly contrast-enhanced and T2-prolonged bone masses: Initial experience.

PURPOSE: To determine whether quantitative diffusion-weighted imaging (DWI) is useful for characterizing poorly contrast-enhanced and T2-prolonged bone masses. MATERIALS AND METHODS: We studied 20 bone masses that showed high signal intensity on T2-weighted images and poor enhancement on contrast-enhanced T1-weighted images. These included eight solitary bone cysts, five fibrous dysplasias, and seven chondrosarcomas. To analyze diffusion changes we calculated the apparent diffusion coefficient (ADC) for each lesion. RESULTS: The ADC values of the two types of benign lesions and chondrosarcomas were not significantly different. However, the mean ADC value of solitary bone cysts (mean +/-SD, 2.57 +/- 0.13 x 10(-3) mm(2)/second) was significantly higher than that of fibrous dysplasias and chondrosarcomas (2.0 +/- 0.21 x 10(-3) mm(2)/second and 2.29 +/- 0.14 x 10(-3) mm(2)/second, respectively, P < 0.05). None of the lesions with ADC values lower than 2.0 x 10(-3) mm(2)/second were chondrosarcomas. CONCLUSION: Although there was some overlapping in the ADC values of chondrosarcomas, solitary bone cyst, and fibrous dysplasia, quantitative DWI may aid in the differential diagnosis of poorly contrast-enhanced and T2-prolonged bone masses.

Adolescent↗
PubMed2006

Ectopic cervical thymus in an infant.

We report a case of accessory cervical thymus presenting as a unilateral neck mass in a 2-month-old boy. Ultrasonography (US) showed a mass isoechogenic to muscle in the left neck. Computed tomography (CT) revealed a well-defined, mildly enhanced mass located anterior to the sternocleidomastoid muscle, anterolateral to the carotid sheath, and posterior to the submandibular gland. On magnetic resonance imaging (MRI), the mass was isointense to muscle on T1-weighted images and hyperintense to muscle on T2-weighted images. Diffusion-weighted images showed relatively low apparent diffusion coefficient (ADC) values, and the mass was slightly enhanced after administration of contrast material. We suspected ectopic thymus, but we could not exclude the possibility of a malignant lesion. Therefore, the tumor was surgically resected. The histological diagnosis was ectopic cervical thymus. Ectopic thymus should be included in the differential diagnosis of a submandibular or cervical mass in infants. US and MRI can provide useful information for the diagnosis of ectopic cervical thymus.

Biomarkers, Tumor↗
PubMed2006

Improvement of low-contrast detectability in low-dose hepatic multidetector computed tomography using a novel adaptive filter: evaluation with a computer-simulated liver including tumors.

PURPOSE: The purpose of this study was to investigate how much radiation dose can be reduced without loss of low-contrast detectability with a newly developed adaptive noise reduction filter in hepatic multidetector computed tomography (MDCT) scans by using a computer-simulated liver phantom. MATERIALS AND METHODS: Simulated CT images, including liver and intrahepatic tumors, were mathematically constructed using a computer workstation to evaluate low-contrast detectability by the observer performance test. Milliampere second for construction of simulated images were 60, 80, 100, and 120 mAs (low dose) and 160 mAs (standard dose) at 120 kVp. Images with 60, 80, 100, and 120 mAs were postprocessed with the adaptive noise reduction filter. A total of 432 images were prepared and receiver operating characteristic (ROC) analysis was performed by 5 radiologists. The detectability of simulated tumor by radiologists was estimated with the area under the ROC curves (Az values). In addition, we visually evaluated CT images of 15 patients with chronic liver damage for graininess of the liver parenchyma, sharpness of the liver contour, conspicuity and marginal sharpness of the liver tumors, and overall image quality. RESULTS: The mean Az value at 0.777 (60 mAs), 0.828 (80 mAs), and 0.844 (100 mAs) without filter was significantly lower than that of 160 mAs without filter (P < 0.001, 60 mAs; P = 0.010, 80 mAs; P = 0.040, 100 mAs). There was no statistical difference between the mean Az value at 80 mAs with and 160 mAs without the adaptive noise reduction filter (P = 0.220) and 100 mAs with and 160 mAs without the adaptive noise reduction filter (P = 0.979). In the visual evaluation of patient livers, there was no statistical difference in the graininess and sharpness of the liver, the conspicuity and marginal sharpness of the tumor, and the overall image quality between standard-dose and filtered low-dose images (Wilcoxon signed rank test, P > 0.05). CONCLUSION: The radiation dose can be reduced by 50% without loss of nodule detectability by applying the adaptive noise reduction filter to simulated and patient liver images obtained at MDCT.

Aged↗
PubMed2006

Quantitative analysis and effect of attenuation correction on lymph node staging of non-small cell lung cancer on SPECT and CT.

OBJECTIVE: The purpose of our study was to assess quantitative indexes and the effect of attenuation correction on the evaluation of lymph node metastasis in the staging of non-small cell lung cancer (NSCLC) using fused thallium-201 SPECT/CT images. MATERIALS AND METHODS: We evaluated 156 lymph nodes (66 metastatic, 90 nonmetastatic) from 29 patients with NSCLC. Using our combined SPECT/CT system, all patients underwent 201Tl SPECT and CT examinations immediately (early images) and 3 hr after (delayed images) the injection of 201Tl. SPECT images were reconstructed with and without attenuation correction. For the quantitative evaluation of lymph node metastasis, we calculated the early ratio, the delayed ratio, and the washout ratio for SPECT images and the short-axis diameter for CT images. Receiver operating characteristic (ROC) analysis was performed in each index for the differentiation between metastatic and nonmetastatic lymph nodes. Visual analysis was also performed by two experienced radiologists. RESULTS: The area under the ROC curve (A(z)) showed that early ratio and delayed ratio were superior to short-axis diameter for the assessment of lymph node metastasis. In addition, early and delayed ratios on attenuation-corrected images were superior to those ratios on images without attenuation correction. However, the A(z) value for washout ratio was smaller than that for short-axis diameter. Early ratio on attenuation-corrected images was the most useful index (A(z) = 0.94). The sensitivity, specificity, and accuracy for early ratio on attenuation-corrected images were 78.8%, 94.4%, and 87.8% for the diagnosis of lymph node metastasis and 84.6%, 100%, and 93.1% for clinical staging (N0-N1 vs N2-N3), respectively. Fused images showed significantly higher diagnostic accuracy than CT images on visual analysis. CONCLUSION: Quantitative assessment using fused SPECT/CT images is useful for the diagnosis of lymph node metastasis in patients with NSCLC.

Adult↗
PubMed2006

16-MDCT aortography with a low-dose contrast material protocol.

OBJECTIVE: The objective of our study was to evaluate whether a low-dose contrast material (CM) protocol with a saline flush might provide sufficient contrast enhancement in aortoiliac 16-MDCT angiography. SUBJECTS AND METHODS: Forty-five patients were divided into two groups on the basis of the CM (300 mg I/mL) administration protocol: group 1 (23 patients) received 100 mL of CM at 3.0 mL/sec; and group 2 (22 patients), 50 mL of CM at 3.0 mL/sec followed by a 20-mL saline flush at 3.0 mL/sec. All patients underwent 16-MDCT angiography of the entire aortoiliac region. Seven regions of interest (ROIs) were drawn from the ascending aorta (ROI 1) to the external iliac artery (ROI 7). Quantitative analysis was performed by calculating the mean aortoiliac attenuation and the mean difference between the maximum and minimum attenuation values. Vascular enhancement of the renal arteries was visually assessed using 2D and 3D postprocessing techniques. RESULTS: The mean aortoiliac attenuation in group 1 was 314.3 +/- 45.9 H and that in group 2 was 306.1 +/- 35.0 H. The difference was not statistically significant. Adequate mean aortoiliac attenuation was achieved in 95.7% (22/23) and 95.5% (21/22) of patients in groups 1 and 2, respectively. The difference was not statistically significant. The mean difference between the maximum and minimum attenuation values was significantly smaller in group 1 (41.3 +/- 16.8 H) than in group 2 (57.2 +/- 25.3 H). The renal arteries were assessable in all patients in both groups. CONCLUSION: This protocol of 50 mL of CM with a saline flush provides attenuation comparable to that obtained with the 100 mL of CM in aortoiliac 16-MDCT angiography.

Aged↗
PubMed2006

Simulation of aortic peak enhancement on MDCT using a contrast material flow phantom: feasibility study.

OBJECTIVE: The objective of our study was to develop a flow phantom simulating aortic peak enhancement after the injection of contrast material on CT and to investigate the validity of the flow phantom by comparing the time-enhancement curves obtained for the flow phantom and humans. MATERIALS AND METHODS: We developed a flow phantom simulating the enhancement pattern of the aorta after the injection of contrast material. In protocols 1, 2, and 3 of the phantom study, 90, 102, and 150 mL of iohexol, respectively, was administered over 35 sec. In protocol 4, 102 mL of iohexol was administered over 25 sec. In phantom protocols 1', 2', and 3', the dose and contrast injection duration were the same as in protocols 1, 2, and 3; however, saline (10 mL) was injected during the 20 sec after contrast delivery. In the human study, 20 patients were randomized into four groups: Groups A, B, and C received 1.5, 1.7, and 2.5 mL of iohexol per kilogram of body weight, respectively, over 35 sec; and group D received 1.7 mL/kg over 25 sec. In patient groups A, B, C, and D, phantom protocols 1, 2, 3, and 4 were used, respectively. Single-level serial CT scans were obtained using a 16-MDCT scanner on the simulated and real aortas after the injection of contrast material. Time-enhancement curves of simulated and real aortas were generated, and aortic peak times and aortic peak enhancement values were calculated. RESULTS: Aortic peak enhancement and aortic peak times in protocols 1-4 and 1'-3' of the phantom study were 2-8% larger and 6-18% longer, respectively, than in the corresponding patient study. The shape of the time-enhancement curves before aortic peak time in protocols 1-3 and 1'-3' of the phantom study closely resembled that of the corresponding patient study. After the aortic peak time, the shape of time-enhancement curves in protocols 1, 2, and 3 of the phantom study was different from the corresponding patient study; however, it was similar in phantom protocols 1'-3' and the corresponding patient study. In all four phantom protocols, the difference between maximal and minimal aortic peak enhancement was less than the SD of the corresponding patient study. CONCLUSION: The level of peak aortic enhancement and the time to peak aortic enhancement were similar in the phantom and human studies when we used our different contrast injection protocols for MDCT.

Aged↗
PubMed2006

Lower tube voltage reduces contrast material and radiation doses on 16-MDCT aortography.

OBJECTIVE: The purpose of our study was to compare aortic CT angiography performed at a low tube voltage and reduced dose of contrast material with standard-voltage, standard-contrast-dose CT angiography. SUBJECTS AND METHODS: We evaluated 74 patients for aortic disease on MDCT angiography (collimation, 16 x 1.5 mm; beam pitch, 0.9). In 36 patients, we used the standard tube voltage (120 kVp) and a contrast dose of 100 mL (300 mg I/mL) (protocol 1), and in the remaining 38 patients we applied a reduced tube voltage (90 kVp) and a contrast dose of 40 mL (300 mg I/mL) (protocol 2). The patients' weights, CT attenuation of the aorta, visualization of the celiac axis and renal artery, and graininess and streak artifacts on transverse CT scans were evaluated and recorded for each data set. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were also measured. For statistical analysis, we used the two-tailed Student's t test and logistic regression; agreement between measurements recorded independently by two blinded reviewers was assessed using Cohen kappa statistics. RESULTS: In both protocols a negative correlation was seen between patient weight and CT attenuation. In three protocol 1 patients weighing more than 70 kg, CT attenuation was less than 200 H. No difference was seen between the two protocols with respect to mean attenuation of the aorta (p = 0.13) or visualization of the celiac axis and renal artery (p = 0.35 and 0.60, respectively). Although the SNR and CNR were significantly higher in protocol 1 than in protocol 2, qualitative evaluation of graininess and streak artifacts showed no statistically significant difference (p = 0.15 and 0.48, respectively). Interobserver agreement for quality assessments was within an acceptable range (kappa = 0.42-0.80). CONCLUSION: Low-contrast and low-voltage scans are appropriate for lighter patients (< 70 kg in body weight) with aortic disease. Moreover, this method is particularly valuable for follow-up studies of heavier patients (> 70 kg) with renal dysfunction.

Adult↗
PubMed2006

Cardiac 16-MDCT for anatomic and functional analysis: assessment of a biphasic contrast injection protocol.

OBJECTIVE: The purpose of this study was to determine the optimal contrast injection protocol for clear delineation of the endocardial and epicardial contours and coronary vessels in anatomic and functional imaging with cardiac 16-MDCT. SUBJECTS AND METHODS: Thirty-eight patients were allocated to three groups according to contrast injection protocol: a long-duration biphasic protocol in which diluted contrast material was used in the latter phase (protocol A, 13 patients); a uniphasic protocol with saline flush (protocol B, 12 patients); a uniphasic protocol without a flush (protocol C, 13 patients). Six regions of interest were drawn within the left ventricle (LV), right ventricle (RV), and interventricular septum along the z-axis. Mean ventricular attenuation, mean difference between maximum and minimum ventricular attenuation, and ventricular-myocardial contrast-to-noise ratio (CNR) were calculated. Attenuation and visualization of the coronary vessels also were compared. RESULTS: The difference between maximum and minimum RV attenuation was significantly smaller in group A (58.1 H) than in groups B (179.5 H) and C (157.0 H). RV-myocardial CNR was significantly higher in group A (9.0) than in group B (5.5). The mean LV attenuation, difference between maximum and minimum LV attenuation, and LV-myocardial CNR were not significantly different among three groups. In protocol A, both endocardial and epicardial contours were clearly delineated, and cardiac functional analysis was feasible in all cases. Average attenuation and visualization of the coronary vessels were not significantly different among groups. The diagnostic accuracies in detection of coronary stenosis were 92%, 93%, and 91%, respectively, for protocols A, B, and C. CONCLUSION: The long-duration contrast injection protocol with diluted contrast material is optimal for assessing the coronary vessels and cardiac function.

Aged↗